Magnetic carbonyl iron suspension with organoclay additive and its magnetorheological properties

Soft magnetic carbonyl iron (CI) based magnetorheological (MR) fluids containing three different loadings of submicron-sized organoclay were prepared. The MR characteristics were measured via rotational and oscillatory tests, in which the flow curves exhibited a non-Newtonian behaviour for all investigated samples. The dynamic yield stress change was measured as a function of magnetic field strength by adopting a linear fit of the relation of log (τy) proportional to log (H), which was originally applied for electrorheological fluids. The viscoelastic performances of the pure CI suspension and the CI/organoclay suspensions showed the existence of a solid-like character. The sedimentation ratio was also investigated to confirm the role of sub-micron organoclay particles on the MR properties, in which the dispersion stability of pure CI was improved with increasing the content of organoclay in the CI suspension.